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Vintage Stax repair and maintenance - Page 3

post #31 of 167
Thread Starter 

 

I bring back from the Stax thread this SR-X/Mk3 repair case.

 

[I said]

 

I took the plunge and opened the SR-X/Mk3 drivers. I mean, not just the earcups, but the drivers (diaphragm and stators).

 

I did it because the sound wasn't up to my expectations. My goal was (and still is) to clean inside and recoat the diaphragms.

 

My first surprises were :

 

1. Both diaphragms were firmly stuck to one stator. I mean stuck like glue...

2. There were small holes in the diaphragms

3. There's a kind of large foil ring that's missing in one driver, compared to the other.

 

Could you help me please.

 

[Wachara said]

 

I wouldn't bother to change the diaphragm if the holes are small. If you want to recoat the diaphragm, clean the diaphragm with alcohol or acetone. Make sure there is no dust on the surface. You only need to coat the the diaphragm one side. It's normal to see that the diaphragm is glued to one of the stators. Actually what you see is the diaphragm glued to a spacer which is glued on a stator.  ;)

 

Can you take some pictures to show us?  I don't understand what you meant by a large foil ring.

 

[Here's my answer]

 

I've damaged one of the diaphragms doing the operation, so I've decided to change both, or at least try to...

 

I've found mylar 2 microns. I still have to decide for the coating stuff.

 

Now, I have to figure how to unglue the two metal spacers that sandwiches both diaphragms. I'll try with a sharp knife, but maybe a solvent would be better ?

 

The diaphragms were really stuck to a stator on their complete surface. Once unstuck, tha stator was printed on the diaphragm.

 

I'll get back with some pictures...


Edited by Headdie - 3/31/12 at 7:36am
post #32 of 167

If the diaphragm is stuck to one side of the stators, then, yes, you won't have good sound.  The sound you hear will be quite distorted and no dynamic.  The bass is gone too.

 

The problem is that over times, the glue gluing the diaphragm looses its strength.  If you haven't strip apart the diaphragm, you might want to try using a hair dryer and use its hot air to do some heat treatment on the diaphragm.  This will shrink the diaphragm somewhat and give more tension to the diaphragm surface.

 

I definitely want to see some pictures.

 

Could you also make some measurements?  I like to know what the diameter of the diaphragm is.

 

Wachara C.

 

 

post #33 of 167
Thread Starter 

The two drivers,

 

IMG_2588.JPG

 

One driver opened,

 

IMG_2592.JPG

 

How to assemble it :

 

Top left in bottom left,

then bottom right in bottom left,

then top right on top of it.

 

Diameter of the stators is 48 mm

Inside diameter of the diaphragm is 55 mm

Outside diameter of the diaphragm is 59 mm

 
The thin foil part (top left) is missing in the second driver.
I wonder if it could be a spacer for perfect fitting...
 
You can see the small holes in the membrane.
The membrane in the other driver is a wreck and can't be saved.
 
The membrane is sandwiched between two spacers.
You can see one on top of the membrane (bottom right).
The second one is under the membrane (bottom right).
 
I still have to find a way to unglue these two spacers,
so I can replace the membrane.
 
Any help is welcome,

Edited by Headdie - 3/31/12 at 3:49pm
post #34 of 167

Did you mention in your earlier post that one of the rings is missing?  Which one is it?  Is it the one on the top left?

 

Can you check to see if the groove that fits the spacer in have the same depth on both?  They are the ones on top right and bottom left.

 

Yes, you need to find a way to take apart the spacers that sandwich the diaphragm.  When you glue the diaphragm back, you don't need to do the same.  If one ring is strong enough to hold the diaphragm, you don't need to glue the other one.  If I were you I would try to use this diaphragm that you show first.  I would try to coat the diaphragm with new coating and try to see if it works.  Then you can decide whether you really want to change it.

 

Best regards,

 

Wachara C.

 

 

 

 

post #35 of 167
Thread Starter 

It's nice to have a coach on the other side of the planet smile.gif

 

I did it. A sharp knife was enough to take the spacers apart.

 

Effectively, top left is missing in one of the drivers. Now, I'll get a better tool for precision measurements and I'll tell you.

post #36 of 167

I am curious as how the drivers are biased.  Can you take a few more close up pictures?  I like to see the connection where the diaphragm is given its bias voltage.  

 

Wachara C.

post #37 of 167
Thread Starter 

You won't see it easily, at least from the picture I can take...

 

The bias is applied to one of the spacers sandwiching the membrane.

It is not soldered to the spacer, but simply applied by a spring/pressured contact.

 

If you look at my first picture,

t 's the 12 o'clock contact that relay bias to the spacer through the plastic...

 

Tell me if my english isn't clear enough,


Edited by Headdie - 4/1/12 at 8:56am
post #38 of 167

I do not understand why there is this other ring that is missing on the other side.  Are the grooves not of the same dept on the Top Right and the Bottom Left?  

 

Wachara C.

post #39 of 167
Thread Starter 

They seem to be. The foil/missing piece is very thin. I can't even measure its thickness. I'd say between aluminum foil and the diaphragm thickness.

 

If it's for fitting purpose, it's for precision adjustement. Anyway, I'll put it back to its place when I'll reassemble it.

 

Actually, I plan to begin the repair with the broken diaphragm. If I can rebuild it (and I can't see why I couldn't), then I'll rebuilt the second also, to have them equal.

 

I've found mylar 2 microns with/without Elvamide on eBay.

 

I'm tempted to buy it with Elvamide, even if it's humidity sensible.

 

I'm still new to this thing, but here's the rational : No coating stuff seems to be perfect. People on the internet are splitted between different coating material. If I face problems with Elvamide, then I'll try something else.

 

By the way, with a 20 meter roll of mylar, chances are that I'll try to build/rebuild electrostatic pannels...

 

The fun begin !

post #40 of 167

Do you know how to prepare Elvamide?  From what I know, it's not that easy.  If I remember it correctly, you have to dissolve it in heat and alcohol.  It takes a lot of time to do it right.  If you already have the computer screen cleaning gel, you should give it a try first.  That's the easy and very effective way to do it.  Trust me on that.

 

2 microns Mylar is good.  Go for it.

 

Best regards,

 

Wachara C.

 

 

post #41 of 167
Thread Starter 

Thank you very much Wachara.

I'll continue this little project the next weekend.

Then, I'll try the gel on the remaining diaphragm.

Meanwhile, I'll get me a multimeter.

Have a nice day,

post #42 of 167

I sometimes wonder how people made those holes on the mylar membrane... what in the world did they try to run these headphones off? Good luck with the repair, I've found that SR-Xmk3s tend to be in worse condition than the average vintage Staxen, even though they use exactly the same driver as the SR-5.

 

How would you re-glue the membrane to the spacers, by the way?

post #43 of 167
Thread Starter 

Good question ! I was to ask Wachara... I've read that some people use some kind of epoxy...

post #44 of 167

Hi!

 

The best glue I have found so far is rubber glue (contact cement).  Please read my post here: http://www.head-fi.org/t/498292/my-diy-electrostatic-headphones/210#post_8017972

 

About the holes on the diaphragm, I think the original owner must have cranked up the volume so high that it burned through the diaphragm.  It's pretty easy to do that with a powerful amp running through the step up transformer to the headphones. 

 

Wachara C.

 

post #45 of 167

Most of these are due to the massive volume mismatch between the headphones and speakers connected to the loopout.  Forget to turn down the volume before turning the switch and you get 400+Vp-p- on the stators and the diaphragm starts to arc. 

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